> Killing some processes to free up memory

This section is disregarding a key lore element, the inhabitants of the grid are programs. Killing a process in this context more likely has an interpretation of an attempt to stop an individual such as the villain Clu. I would say an alternative explanation is is more story based, with Kevin Flynn trying to stop Clu from the outside world but being unable to and instead taking the last resort of entering the grid when he knows it would be dangerous.